answer an increasingly urgent question: How
can we help forests keep up with human-caused
climate change? In plots like this, from Northern
California to the Yukon border, O’Neill, a forester
for the British Columbian government, and his
colleagues have planted seedlings from larch
and other species collected from groves along
the West Coast to test the concept of assisted
migration. They want to see how far and how
quickly foresters need to move tree populations
north to keep pace with climate change.
The problem is simple, says Cuauhtémoc
Sáenz-Romero, a researcher at the Universidad
Michoacana de San Nicolás de Hidalgo, in Mex-
ico. “Climate is moving ... and trees cannot walk.”
Since the late 19th century, when humans
started burning fossil fuels and pumping huge
quantities of carbon dioxide into the atmo-
sphere, average global temperatures have risen
about 1.1 degrees Celsius (2.4 degrees Fahr-
enheit). On the current emissions trajectory,
they’re likely to rise at least that much more in
the coming decades.
On average worldwide, forests can expand
their range up to 3,000 feet or so a year, as treelets
often track their preferred climates toward the
poles, or uphill. To keep up with the pace of
today’s change, they’d need to be going six to
10 times as fast. In British Columbia the dispar-
ity is even greater: A 2006 study suggested the
province’s climate zones would move northward
about six miles a year.FIXING FORESTS 123